A few years back I did a bit of research on milkfloats running a (PWM, DC) electronic motor via lead acid battery. I was interested in finding out as to what it is exactly that causes the electronic acceleration sound example found here:

Milk Float Page ::

They are characteristic little vehicles, but I never really got to the bottom of what I wanted to find out. What I did find out however is that the float uses some of the following components:

I believe it runs on DC current
It uses an obviously huge battery (lead acid type)
PWM controlled motor
5 pole variable speed control - no gears just start stop and speed control
Despite its slow speed, it must have heavy duty turnover/torque output.

But getting to the point what component produces the characteristic ramp sound? I assume it is something to do with the PWM controller component and not the motor. However this sound can’t seem to be found on other electronic vehicles…

PWM controlled golf carts do not seem to make the same sound however, so could it be down to the fact that its a large vehicle and requires large load or dont they employ frequency controllers anymore? Wink

I’d be interested to build a smaller electric motor system like this…